Differential diagnosis of proteinuria

The incidence of proteinuria is becoming higher and higher, and many patients are unaware of it even when it occurs. This will cause many patients to miss the best time for treatment. Therefore, regular check-ups are critical. After the examination, you can clearly know whether you have proteinuria, so that you can receive treatment early.

The commonly used method for laboratory examination of urine protein in the past has now been replaced by the sulfosalicylic acid method. This method is simple and does not require any reagents.

Method: Take a glass test tube and pour the urine to be tested to two-thirds of the tube. Add a few drops of 2% acid or vinegar. Hold the bottom of the test tube diagonally with your thumb and finger. Place it on a flame (such as an alcohol lamp) to directly heat the urine at the top of the test tube. Turn the test tube frequently until the upper part boils. Observe whether there is turbidity or precipitation and coagulation. Determine the plus sign according to the degree as follows. In order to rule out a false positive caused by turbidity not being caused by protein, 2 to 3 drops of acetic acid or a dozen drops of vinegar should be added. If the turbidity does not disappear, it is a positive reaction, indicating that it is protein.

Test strip method

The test paper is a test paper prepared in advance by a reagent factory specifically for qualitative testing of urine protein and can be purchased at a drug store. The test paper is soaked with reagent drugs and turns blue when it comes into contact with protein. It is also accompanied by a standard color plate, which is used for comparison based on the measured depth of blue. The method is relatively simple. Take a test paper, dip it into the urine to be tested, take it out immediately, and observe whether there is a blue display for about 10 to 20 minutes. If there is no change, it is negative and appears blue, that is, the color

Alkaline urine may give a false positive result. Therefore, before the test, check the pH value of the urine with litmus paper. If it is alkaline (above pH 7.0), add a few drops of acetic acid to make the urine acidic before the test. The above three methods are qualitative tests for urine protein, which only indicate whether there is protein in the urine and the relative amount, but cannot tell the exact amount. If you want to know how much protein is excreted every day, you can do a quantitative measurement. You need to collect urine for 24 hours and do a quantitative protein measurement.

The urine protein content was estimated based on the turbidity reaction as follows:

Urine protein <0.1g/L: 1;

Urine protein is 0.1-0.2 g/L: ±;

Urine protein is 0.2-1.0 g/L: +;

Urine protein is 1.0-2.0 g/L: ++;

Urine protein is 2.0-4.0 g/L: +++;

Urine protein>4.0g/L:++++.

Normal urine contains trace amounts of protein (24-hour urine protein quantity <150 mg), which cannot be detected by ordinary detection methods and the test result is negative. If it exceeds this range, it can be detected and is called proteinuria. However, since the urine protein test only measures the result of one urine test, it is easily affected by the concentration and dilution of the urine and often cannot accurately reflect the degree of proteinuria. When the human body excretes strenuous exercise, heavy physical labor, emotional excitement, excessive cold, overheating, or is under stress, the amount of urinary protein excretion may increase. This is called transient proteinuria and will return to normal after a few hours or days.